In the second season of "Sherlock," Professor Moriarty, the criminal mastermind, met his ultimate end. "Sherlock" Season 3 will introduce a new villain that Sherlock (Benedict Cumberbatch) must outsmart.

Charles Augustus Magnussen, played by Lars Mikkelsen, will be the nemesis in the third season of "Sherlock."

Charles Augustus Magnussen is expected to be more sinister than Professor Moriarty. Steven Moffat, co-writer of "Sherlock," said to Radio Times that the new nemesis is "terrifying." He did not provide much information about the new villain, but said that "you'll know the angle we've taken on it within seconds of it beginning..."

Charles Augustus Magnussen is loosely based on Sir Arthur Conan Doyle's villain, "Charles Augustus Milverton." In Sir Doyle's "The Adventure of Charles Augustus Milverton," Sherlock Holmes says to Watson: "He is the king of all the blackmailers. Heaven help the man, and still more the woman, whose secret and reputation and secret come into the power of Milverton. With a smiling face and a heart of marble, he will squeeze and squeeze until he has drained them dry."

Moffat said that they have taken the character from "The Adventure of Charles Augustus Milverton." However, BBC's "Sherlock" draws from the original source and puts its own spin on "Sherlock Holmes" stories and characters. Likewise, the character of Charles Augustus Magnussen will not be exactly like Charles Augustus Milverton.

"We've drawn from that story (The Adventure of Charles Augustus Milverton] but, as ever with our show, what we drew and how we do it and how we find equivalences, [you'll have to wait and see]," Moffat said to Radio Times. "Sometimes, as you know, we flip things and make them the other way round. We do all those things."

The first episode of "Sherlock" Season 3 is "The Empty Hearse." It is written by Mark Gatiss and directed by Jeremy Lovering. Lovering said to Click "I think what Sherlock did was put me back in that space where it was crafting something that was already written, the characters were created by Benedict, Martin, Mark, Steven and obviously Conan Doyle. So they had the characters pretty well wrapped up and Mark wrote the script that I did and so the script is tight and there's a precedent."